FI64794C - FIBERGLASSAMMANSAETTNING - Google Patents

Description

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The present invention relates to a glass composition for the production of fibers for glass wool insulation. The glass composition according to the invention is particularly well suited for the preparation process according to the so-called Johns-Ma nvi Herne method, at which the utilized process apparatus does not withstand too high temperatures.

In conventional manufacture of such fibers, molten glass pulp is pressed due to the centrifugal force through shark in a rotating spinning disk. In order for satisfactory fibers to be obtained, it is desirable that the glass meets certain criteria. Thus, the melting temperature and fiber forming temperature of the glass should be low, thereby giving the spin plate as long a life as possible. The melting temperature is denoted as the so-called log 2 temperature, ie the temperature at which the logarithm of the glass viscosity measured in Poise (or deciPascal second, dPas) is 2, while the fiber formation temperature is correspondingly stated as log 3 temperature . On log 2 and layer 3 temperatures can be lowered, this results in an increased service life of the spinning plate and the production loss resulting from the change of spinner plate is reduced. Already lowering log 2 and log 3 temperatures by five or ten degrees means a significant improvement. However, reducing only log 2 temperature and log 3 temperature cannot be done, since the other properties of the glass must be taken into account at the same time.

Other important properties of the glass that must be considered are the liquidity temperature, L, p, which is the temperature above which no crystallization occurs in the glass. In order to avoid crystallisation of the glass in the spin plate with certainty, the liquidity temperature must be 50 ° C below the log 3 temperature. Depending on other factors such as the liquid viscosity, crystallization rate and spin rate, crystallization can be avoided even if said temperature difference is only 30 ° C.

Another important feature of the glass is its chemical resistance. The chemical resistance is measured according to standardized test procedures such as so-called hydrolytic resistance (p-value or DGG value).

If one wants to lower the melting temperature and fiber formation temperature of the glass, it is most convenient to increase the content of CaO, 2020, K2O or. However, an increase in the CaO content results in simultaneously raising the liquidity temperature of the glass, with consequent risk of crystallization in the spin plate. An increased content of Na 2 O, K 2 O or B 2 O 3 results in poor chemical resistance of the glass. It is therefore clear that there is very little opportunity to change the composition in a conventional manner so that improved properties are obtained in the Desired sense without at the same time deteriorating the properties in some other respect.

However, in the invention, the details of which are set forth in the appended claims, a glass composition having substantially improved properties compared to standard glass is obtained quite surprisingly by incorporating ZnO and preferably also Li20 in the glass composition.

The invention is based on the relationship that between certain atomic types in the glass such as Zn-Ca and Li-Na-K there is a certain "anomaly" which plays a crucial role for the physical properties of the glass and which depends on the ion radii of the atoms. For the anomaly to be fulfilled, the difference between the ion radii must be greater than 0.3 A. To improve the physical and chemical properties of the glass, this anomaly in the structure of the glass should be well fulfilled, which means that certain atoms should be included in the glass with special conditions. to each other.

It is against the foregoing background that ZnO is incorporated into the glass according to the invention, thereby changing its physical and especially its chemical properties.

In addition, it is particularly preferred to also incorporate 0-1, and heist 0.1-0.4% by weight Li2O in the glass, which further improves anomaly, greatly reduces viscosity and increases the chemical resistance of the glass.

It is known from Finnish application FI 78 3290 to contain ZnO in an ice cream composition, but this composition is otherwise substantially different from the composition according to the invention. The levels of A 2 O 2, CaO and B 2 O 3, as well as Na 2 O in most cases, are higher in the known composition, while the MgO content is lower or even higher. is also zero. The content of MgO in the composition according to the invention is a critical component for achieving a liquidity temperature.

The fiberglass composition of the invention is characterized by a composition which, by weight, is within the following general limits.

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Weight%

Si02 55 - 65 A1203 1 - 2

CaO 6-9.5

MgO 1-4.5

Na20 13 - 17 K20 0-2 B2 ° 3 1 ~ 7

BaO 0-3

Li20 0-1

Fe203 barriers

ZnO 0.5 - 6

In the invention, it is particularly preferred that the composition of the glass is within the following limits:

Weight%

Si02 53 - 62 A1203 1 - 2

CaO 8-9.5

MgO 2.3 - 3.5

Na20 15 - 17 K20 0-1 B203 5 - 7

BaO

Li20 0.1 - 0.4

Fe203 spar

ZnO 1.5 - 3.5

At an addition of 0.5-6, preferably 1.5-3.5% by weight of ZnO, a very good chemical resistance of the glass according to the invention is obtained. The chemical resistance has even been found to be much better than with the addition of, for example, titanium dioxide in the same amounts to the glass.

In general, a high proportion of alkali in aikai-boro-silicate glass appears to be severely impaired on the glass's cerebral resistance, but when adding ZnO to such glass it is now surprisingly possible that the glass can contain larger amounts of alkali without dr Russian resistance deteriorates ί ·; ι;:.

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The high content of alkali in the glass according to the invention in turn affects the viscosity of the glass in the direction that a more liquid liquid glass is obtained, ie the glass's log 2 temperature and log 3 temperature are lowered, which brings with it several practical advantages, such as lower fiberization. temperature, thereby increasing the life of the vibration apparatus and saving energy. The lower vibration temperature also gives a better quality product. Furthermore, the glass according to the invention exhibits a lowering of the liquid temperature compared to previously used conventional glass, and this reduction has the effect of significantly reducing or eliminating the risk of crystallization of the glass in the spin plate. In addition, the glass of the invention exhibits good chemical resistance, as evidenced by the values of hydrolytic resistance in the following examples.

A further advantage of the invention is that readily available and inexpensive ZnO-containing starting materials can be used. Thus, there is no requirement to use absolutely pure ZnO as the starting material for the glass ZnO content, but every ZnO-containing material is usable.

The invention will be illustrated in the following by some illustrative but non-limiting examples. EXAMPLES 1-4

Three pieces of ZnO-containing glass according to the invention were prepared. As a comparison, a conventional alkali borosilicate glass used in practice was prepared, hereinafter referred to as standard glass.

The compositions for the standard glass and for the glass according to the invention, as well as the glass properties with respect to log 2, log 3, liquid viscosity and chemical resistance (P SIS 136 321) are presented in Table 1.

TABLE 1

Oxide Example 1 Example 2 Example 3 Example 4 (standard glass)

SiO2 63.0 62.6 59.2 56.4 A1203 2.5 1.5 1.5 1.5

CaO 8.8 9.1 9.1 9.1

MgO 3.5 3.5 3.5 3.5

Na20 14.7 15.9 15.9 15.9 K20 1.0 0.6 0.6 0.6 B203 6.5 6.9 6.9 6.9

BaO - ---

Li₂O - 0.2 0.2 - /

Fe2 O3 0.2 0.1 0.1 0.1

ZnO - 0.5 3.0 6.0 log η 2 (° C) 1270 1200 1187 1172 log η 3 (° C) 1060 997 992 990 LT (° C) 960 948 920 913

Liquid liquid. 3,699 3,353 3,528 3,617 P SIS v 136232 1.0 1.5 0.9 0.8

Claims (2)

6 4 7 9 4 1. Fiberglass composition with good chemical resistance and preferably up to 50 ° C lower liquid temperature than log 3 temperature, characterized in that it has the composition weight% SiO2 55 - 65 A1203 1-2 CaO 6-9.5 MgO 1-4.5 Na2 O 13 - 17 K20 0-2 B2 ° 3 1 - 1 BaO 0-3 Li20 0-1 Fe203 sparse ZnO 0.5-6 Li20 0.1 - 0.4 Fe203 sparse ZnO 1.5 - 3.5